1. Field of the Invention
The present invention relates to a front fork housing with a both-side rod type damper therein to be used for a motorcycle and the like.
2. Description of the Related Art
There are, structure-wise, two types of dampers, namely a one-side rod type having a rod protruded from one end of a cylinder and a both-side rod type having rods protruded from both ends of the cylinder.
Of the one-side rod type damper, an effective volume of oil chambers on both sides interposing a piston between them varies by a penetrating or retracting volume of the rod into or out of the damper when the damper is operated in extending or retracting movement. Accordingly, in order to absorb the varied volume thereof, a reservoir having an air storage is required. When the air in the reservoir is mixed with working oil, so-called aeration is caused and the damping force of the damper may become unstable or the like.
To the contrary, with the both-side rod type damper, since the volumes of the oil chambers of both sides of the piston varies respectively by the same quantity (when the oil chamber of one side expands, the oil chamber of the other side contracts) at the time of the extending or retracting operation of the damper, there is no variation in total quantity of the working oil in both of the oil chambers, therefore, there is no necessity of escaping the surplus or supplementing the shortage of the working oil, and thus the above-mentioned reservoir becomes unnecessary, and as a result, the damping force characteristic is stabilized.
A front fork housing the both-side rod type damper therein is proposed in JP-2004-293720A and JP-2004-293660A.
Since the both-side rod type damper has the rods protruding from both ends of the cylinder, slidability of the rod at a bearing which supports each of the rods at both ends of the cylinder is apt to be deteriorated when the concentricity of the rod is lost, when the rod is inclined relative to the cylinder, or the like. The former intends to eliminate this problem by movably coupling one of the rods in the radius direction relative to the piston.
Further, since the both-side rod type damper is arranged inside the front fork, it is troublesome to inject the working oil into the damper when filling the working oil into the front fork in the final process of manufacturing in a factory.
In the latter above-mentioned, a check valve is provided at a part of the damper, and filling of working oil is performed by absorbing the working oil filled in the front fork into the damper through the check valve by the extending or retracting operation of the damper. Thereby the filling operation of the working oil is made easy.